These demos almost never involve real hardware. It's so much easier to do interoperability when all it takes to make two devices communicate is to draw a dotted line between them on a slide. And when the demos do involve real hardware, it's usually all from one vendor, and only within a constrained universe of uses.Link
In reality, it's bloody hard to get any two technologies to talk to each other successfully. Remember how hard it was to get your new wireless card, printer or DVD recorder to work? Now, imagine that these technologies had been deliberately designed not to work with each other - except under the exactly correct circumstances.
Microsoft's PlaysForSure platform is typical of this. All such devices, "certified" to work with each other, barely ran on their own. And God help you if you tried to connect them to a competitor's device (even Microsoft's Zune won't handle PlaysForSure music).
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.